This invention relates generally to tools and methods for managing fluid flow in wells, particularly oil or gas wells. A particular implementation of the tool of the invention is a unitary flow control device that can function as a valve, a fluid flow sensor and meter, an electrical generator, and a pump.
In the oil and gas industry, well and reservoir management is an important aspect of efficient and economical production of oil and gas. Fluid flow, such as of the oil and gas being produced, needs to be monitored and controlled. There are various flow sensing devices, flow metering devices and valves used in downhole pipe or tubing strings to perform these functions. With changes in the industry, however, there is the need for improved tools and methods.
One of these changes is that more complex wells are being drilled. For example, horizontal wells and wells with multiple lateral bores extending from a main borehole are being drilled to improve hydrocarbon recovery rates at reduced cost relative to drilling multiple individual vertical wells.
Another of these changes is that more and more control is being put downhole to improve recovery to cost ratios. A presently evolving area uses intelligent tools applying microprocessor and computer technology in the borehole. These and other types of tools require some source of electricity to operate. Typically these sources have included power generating equipment at the surface with wireline connections to the downhole tool or self-contained downhole sources such as batteries contained in the tools themselves. To provide another source, there is the need for a downhole generator that is powered by a well's own flowing fluid.
As a specific situation arising in well and reservoir management, consider an oil or gas well having a main borehole from which several lateral boreholes extend. In this, as with other structural types of oil or gas wells, undesirable water may be produced with desired hydrocarbons. The water needs to be separated from the hydrocarbons, and in at least some instances, injected back into the well or into a disposal well. This typically requires producing the entire stream to the surface from which the well has been drilled (or to a platform or other watersurface facility for offshore wells), separating the water from the hydrocarbons at the surface, and then returning the separated water to the well or to another well. It would be desirable to be able to do this separating and reinjecting downhole to save the time and expense of producing the water all the way to the surface and then returning it back into the ground. Additionally, if the water could be separated and left downhole, more hydrocarbons could be produced in the volume previously occupied by the water. This might also obviate the necessity of having separator equipment at the surface and of having a separate injection well or other water disposal system. Accordingly, there is the specific need for an improved tool and method with which to perform downhole water separation and reinjection. More generally, there is the need for an improved tool and method that can be used downhole to control and monitor fluid flow. There is also the need for such a tool to have the capability of generating electricity in response to fluid flow in a well, such that the electricity can be used in the control aspect as needed, for example.